Granular explosive molding powder



March 16, 1965 5, wRlGHT 3,173,817

GRANULAR EXPLOSIVE MOLDING POWDER Filed 001}. 51, 1962 70/ BINDER EXPLOSIVE IZ SOLVENT GRANULATOR FILTER 2O DRYER SaB. right INVETOR.

3,173,817 United States Patent Ofilice 16,

New Jersey Filed Oct. 31, 1962, Ser. No. 234,467 13 Claims. (Cl. 149-2) This invention relates to the manufacture of explosive compositions. More particularly, it relates to a method of granula'ting plastic-bonded explosives.

This application is a continuation-in-part of my copending applications Serial No. 203,079, now Patent No. 3,138,501, filed June 18, 1962, and Serial No. 50,311, filed August 18, 1960. I Water-insoluble plastic-bonded explosives include DATB (diaminotrinitrobenzene), RDX (cyclotrimethylenetrinitramine, cyclonite, Hexogen), HMX cyclotetramethylenetetranitramine, homocyclonite, Octogen) and the like. Known methods of making such explosives include dispersion of the explosive in a water-miscible solvent solution of a binder followed by precipitation of the binder by addition of quench water or a precipitating agent and pressure extrusion of a plasticized binder followed by incorporation in the explosive as small lumps. In these procedures difiiculties are sometimes encountered in producing a product of suificiently high particle and bulk density and particle uniformity to be acceptable for most explosive uses. The production of a high bulk density plastic-bonded explosive of optimum granule size, porosity and texture in a minimum number of substantially trouble-free steps therefore represents a highly desirable result.

One object of the present invention is to provide a plastic-bonded explosive of maximum bulk density and optimum granulation characteristics. Another object of this invention is to provide a method of producing a plastic-bonded explosive of enhanced bulk density and increased uniformity of dispersion of the explosive. A further object is to provide a method for preparing an explosive molding powder of especially high bulk density. These and other objects will be apparent hereinafter.

In its broader aspects, my invention involves the use of a binder solvent in coating a binder substantially uniformly over the surface of granules of a water-insoluble plastic-bonded explosive, The explosive is slurried in Water. In a preferred embodiment an aqueous dispersion of the binder is mixed with the water slurry of explosive and an organic solvent in which the binder is soluble added to the system after precipitation of the binder onto the explosive by addition of a coagulant such as alum, acetic acid, acetone, or gelatin. In an alternative embodiment the binder solvent is used to make a solution of the binder which is mixed with the water slurry of explosive to yield globules of explosive/binder, using in addition a protective colloid such as gelatin, polyvinyl alcohol, gum arabic or the like for controlling particle size, if desired. In both procedures the solvent is removed by distillation to provide hardened granuleswhich are then separated, for example, by filtration, and dried. The binder is an organic resinous thermoplastic polymer such as polyamide, polyacrylate, polyisobu'tylene, polytetrafluoroethylene or a copolymer of chlorotrifiuoroethylene and vinylidene fluoride. Representative of binder solvents which may be used are isobutyl acetate, isobutyl alcohol, butyl acetate, methyl ethyl ketone, butyl alcohol, benzyl alcohol, toluene, xylene, and the like. The solvent may also consist of a mixture of more than one of such solvents.

In a further embodiment my invention involves the use of a water-immiscible solvent, preferably benzyl alcohol, butyl alcohol or toluene in forming a high-bulk plastic-bonded explosive, viz., DATB, HMX, RDX or a mixture of two or more of these three, with an organic resinous thermoplastic polymer, preferably polyamide (low melting, soluble-type), as binder. The preferred solvent is butyl alcohol. As indicated hereinabove, the solvent may be used to form a solution of the binder prior to addition to a water slurry of the explosive or after addition of an aqueous dispersion of the binder to a water slurry of the explosive, preferably after granulation by addition of a coagulant. A plasticizer or other appropriate viscosity or consistency-regulating substance (e.g., motor oil) may be used in conjunction with the binder.

For a more complete understanding of my invention reference is made to the attached drawing which is a part hereof and illustrative of the process of my invention. The drawing is in schematic flow sheet form.

In the drawing, the binder 10 is added to the water slurry of the explosive 12 to form a mixture which is granulated at 14, the solvent being removed at 16 by evaporation. The product is then filtered at 18 and dried at 20 to a high-bulk plastic-bonded explosive granules.

The following examples are illustrative of my invention but are intended to be representative only and not limiting.

Example 1 Prepare a polyhexame'thylene adipamide/butyl alcohol lacquer by dissolving 20 to 50 g. polyamide in 500 g. butylalcohol at -75 C. Place 2,000 g. water and 470 g. diaminotrinitrobenzene (DATE) in a 10-liter still. Adjust agitation to 500-600 r.p.m. and heat the slurry to -75 C. Add, the lacquer solution to the agitated slurry at a rate sutficient to insure incorporation into the explosive/water slurry. The resulting emulsion is agitated until the desired granule size is obtained. The butyl alcohol is vaporized to yield a hardened granule. The slurry is cooled to about 50 C. and filtered. The resulting product contained about 2-10 percent polyhexarnethylene adipamide and about 98-90 percent DATE. The bulk density of the product was about 0.6 to 0.7 gm./ ml. The granules were hard and well formed. The granulation was essentially 100 percent passing US. Sieve No. 18 and esesntially 100 percent retained on US. Sieve No. 80. The granules were pressed into pellets (0.9" dia. x 1" long) at 25,000 p.s.ig. and C. to yield a density of greater than 95 percent of the calculated or theoretical density; the compressive strength was greater than 10,000 p.s.i.

Example II The procedure of Example I was followed except that benzyl alcohol was used in place of butyl alcohol. Granules comparable to those of Example I were pressed into 0.9" x l" pellets having a density of about 96% of the theoretical.

Example III A separate batch of plastic-bonded explosive was prepared. The procedure of Example I was followed except that about 0.1 percent gelatin, based on product weight, was added to the mixture during granulation and the explosive used this time was RDX.

Example IV Slurry 470 g. DATB and 4,000 g. Water in -a-10-1iter still. Add 200 to 500 g. polyhexamethylene adipamide dispersion (10 percent polyhexamethylene adipamide). Mix well and adjust agitation to 300-400 r.p.m. Coagulate the polyhexamethylene adipamide by adding 2 to 3 g. acetic acid dissolved in 100 ml. water. Add 500 ml. butyl alcohol and digest at 30 to 40 C. for 15 to 30 min. Vaporize the butyl alcohol from the system. Cool the batch and filter. The product containing 2-10 percent polyamide and 9890 percent DATB exhibited characteristics comparable to those cited for the product prepared with a lacquer of polyhexamethylene adipamide and butyl alcohol.

Example V Another batch of explosive product was formed using the procedure of Example IV except that about 0.1% poly(vinyl alcohol), based on product weight, was added to the mixture during granulation and the explosive used was HMX.

Example VI Lacquer preparation-Add 12.5 grams polyisobutylene, precut to marble size, to 130 grams toluene. Agitate the mixture at 60-70 C. for 1% hours. Add 8.0 grams motor oil (SAE 10) and 29.5 grams di-(2-ethylhexyl) sebacate and mix well. Cool to 30 C.

Granulatin.Add liters of water to a -liter granulator, adjust agitation and add 150 grams of fine RDX (about 3% retained on USS No. 325 sieve) and 300 grams of coarse RDX (about 50% retained on USS No. 100 sieve). Add 0.1 gram gelatin and heat the slurry to 65 C. Add the lacquer over a 1 to 2 minute period with agitation set at 450 to 500 r.p.m. Heat the mixture to 99.5 to 100 C. Cool the slurry to 60 C. Transfer the slurry toa vacuum filter, remove the water. Dry the product at 5060 C., using a forced air dryer, for 2 /2 hours.

Percent Results: added RDX, percent-89.90 90.0 Binder, percent10.09 10.0

Water, percent-0.0l. Binder content 2.68 percent polyisobutylene. 7.41 percent oil+di(2-ethylhexyl) sebacate. Plasticity-0.004 units.

Example VII The lacquer was prepared as discussed in Example V1 with the exception that 170 grams toluene were used.

Granularion.Add 505 grams RDX (2 parts coarse RDX and 1 part fine RDX) to 5.5 liters of water in a 10- liter granulator. Add 0.2 gram gelatin and heat the mixture to 75 C. The lacquer addition and solvent removal is made according to the procedure of Example VI.

The product was dried at room temperature, to C., by placing the material in open trays. The depth of the material was about /2 inch.

Percent Results: added RDX, percent-90.60 91.0 Water, percent0.l7. Binder, percent-9.23 9.0

Binder content 233- percent polyisobutylene 2.25 6.90 percent oil+di(2-ethylhexyl) sebacate 6.75

Example VIII This batch was processed as discussed under Example V with the exception that the amount of toluene was increased to 200 grams and the amount of water for the RDX/water slurry was reduced from 5 liters to 2 liters.

Percent Results: added RDX, percent-90.40 90.9 Water, percent0.13.

Binder,- percent--9;47' 9.1

4.- Example IX Binder preparation.Add 4.55 liters toluene to a 10- liter still. Heat to 70 C. Add 254.3 grams polyisobutylene, cut in small pieces to facilitate dissolution, and reflux the solvent until solution of the binder is obtained. Cool the solution to 30 C., add 603.8 grams di(2-ethylhexyl) sebacate and 174.8 grams motor oil' (SAE 10); Mix well and transfer the binder to a five-gallon safety can. Prepare two binder batches, as described above, for a 50 pound batch of a composition containing 61% coarse RDX, 30% fine RDX, 2.25% polyisobutylene, 5.31% di-(2-ethylhexyl) sebacatev and 1.44% SAE 10 motor oil.

Granulation.Add 400 pounds water and 30.5 pounds coarse RDX and 15.0 pounds fine RDX to the granulator. Add 0.01 pound dry gelatin and heat the slurry to to C. Add the prepared lacquer at a rate of about /2 gallon per minute. Set agitation at 250 rpm. and heat the slurry to 99 to 100 C. Cool the batch to 50 to 60 C. and drop the material to a vacuum filter. Dry a portion of the product by the following methods: rotary vacuum dryer at 60 C., forced air dryer at 60 to 70 C., and an incorporation kettle at C.

Percent Results: added RDX, percent--90.90 91.0 Binder, percent-8.97 9.0

Water, percenfi0.l8. Plasticity0.004 units. Specific gravity1.65 g./ml.

Example X Binder preparation.-Prepare the binder, in a production scale lacquer pot, according to the method described in Example IX. Use the following amount of materials.

Pounds Polyisobutylene 56 di(2-ethylhexyl) sebacate 133 Motor oil (SAE 10) 39 Toluene 850 Granulation.-The material was granulated according to the procedure outlines in Example IX. A production scale granulator was used. Material used: coarse RDX, 1525 pounds; fine RDX, 750 pounds; water, 20,000 pounds; gelatin, 0.5 pound.

Percent Results: added RDX, percent--91.03 91.9 Binder, percent-8.97 9.0

Water, percent-0.06. Insolubles, percentNone. Plasticity0.010 unit. Specific gravity, g./m1.-1.60.

Example X1 Slurry 425 g. HMX and 2,000 g. water in a 10 liter still. Add 150 g. poly(ethyl acrylate) latex (50% solids) and agitate the mixture for about 5 min. Add 3 g. alum dissolved in about 30 g. water. Heat the slurry to about 99 C. to remove volatiles added to the system with the poly(ethyl acrylate) latex. Cool the material to 50 C. and filter. Granulation of the material was essentially 100% passing U.S. Sieve No. 18 and about 95% retained on US. Sieve No. 100. Bulk density of the material was about 0.6 to 0.7 g./ml.

Example XII Slurry 510 g. HMX andv 2,000 g. water in a 10 liter still. Add 180 g. dispersion of chlorotrifiuoroethylenevinylidene fluoride copolymer (50% solids) and agitate the mixture for 15 min. Add 3 g. alum dissolved in 30 g. water. Heat the slurry to 80 to 82 C., add to g. isobutyl acetate and 1 to 2 g. polyvinyl alcohol. Heat the mixture to' 99 C. Cool to 40 C. and filter.

The product exhibited a bulk density of 0.97 g./ml. and granulation of 100% passing U.S. Sieve No. 4 and 100% retained on U.S. Sieve No. 40.

Example XIII Slurry 425 g. HMX and 2,000 g. water in a liter still. Add 125 g. polytetrafiuouroethylene dispersion. Agitate the slurry for 5 to 10 min. Add 160 ml. n-butyl acetate. Add 1.5 liters acetone over a 2 to 5 min. period. Agitate the mixture for about 5 min. Filter the granulated product. Granulation of the material was essentially 100% passing U.S. Sieve No. 18 and essentially 95% retained of U.S. Sieve No. 50. Bulk density of the product was about 0.6 g./ml.

Examples X I V-X VI The procedures of Examples XI-XIII respectively were followed except that in each case RDX was used in place of the HMX. In every instance the product was of substntially the same properties given for the corresponding plastic-bonded HMX.

From the foregoing description it is apparent that I have provided a novel method for preparing plastic-bonded explosives of increased bulk density and uniformity of distribution of explosive particles.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be efiected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

I claim:

1. A process for the production of a plastic-bonded explosive which comprises uniformly dispersing with mixing an organic resinous thermoplastic polymer binder for a water insoluble plastic-bondable explosive in a dispersion medium for said binder, mixing the resulting dispersion with an aqueous slurry of the plastic-bondable explosive, evaporating medium from the mixture of said dispersion with said slurry with agitation thereby forming a granulated plastic-bonded explosive and filtering" and collecting the granulated plastic-bonded explosive, said dispersion, mixing and evaporating of medium as a process being accompanied by addition of a solvent for said binder.

2. The process according to claim 1 wherein the explosive is selected from the group consisting of diaminotrinitrobenzene, cyclotrimethylenetrinitramine and cyclotetramethylenetetranitramine, the binder is selected from the group consisting of polyamide, polyacrylate, polyisobutylene, chlorotrifluoroethylene-vinylidene fluoride copolymer and polytetrafluoroethylene and the solvent for the binder is a water-immiscible organic solvent.

3. The process according to claim 1 wherein the solvent for the binder is added prior to mixing the dispersion of binder with the aqueous slurry of plastic-bondable explosive and the dispersing of the binder in a dispersing medium for said binder comprises dispersing the binder in a solvent for the binder.

4. The process according to claim 1 wherein the addition of the solvent for the binder takes place after mixinging the dispersion of binder with the aqueous slurry of plastic-bondable explosive.

5. The process according to claim 1 wherein the binder is a low-melting soluble-type polyamide, the explosive is selected from the group consisting of diaminotrinitrobenzene, cyclotrimethylenetrinitramine and cyclotetramethylenetetranitramine and the solvent for the binder is selected from the group consisting is isobutyl alcohol, isobutyl acetate, butyl alcohol, butyl acetate, methyl ethyl ketone, benzyl alcohol, xylene and toluene.

6. The process according to claim 1 wherein the solvent for the binder is a water-immiscible solvent.

7. The process according to claim 1 wherein the binder is a low melting soluble-type polyamide, the explosive is diaminotrinitrobenzene and the solvent for the binder is selected from the group consisting of butyl alcohol, isobutyl alcohol, butyl acetate, isobutyl acetate, methyl ethyl ketone, benzyl alcohol, xylene and toluene.

8. A process for the production of a plastic-bonded explosive of increased bulk density which comprises in successive order:

(1) slurrying an explosive selected from the group consisitng of diaminotrinitrobenzene, cyclotrimethylenetrinitramine and cyclotetramethylenetetranitramine with water,

(2) adding with agitation to the resulting slurry a solution of a binder selected from the group consisting of polyamide, polyacrylate, poilyisobutylene, chlorotrifluoroethylenevinylidene fluoride copolymer and polytetrafiuoroethylene in a Water-immiscible solvent therefor selected from the group consisting of butyl alcohol, benzyl alcohol, isobutyl alcohol, butyl acetate, methyl ethyl ketone, isobutyl acetate, xylene and toluene, the agitation being sufiicient to yield globules of explosive/ binder,

(3) removing the solvent by distillation, thereby providing hardened granules of explosive/binder, and

(4) collecting the hardened granules of explosive/ binder.

9. A process for the production of a plastic-bonded explosive of increased bulk density which comprises in successive order:

(1) slurrying an explosive selected from the group con sisting of diaminotrinitrobenzene, cyclotrirnethylenetrinitramine and cyclotetramethylenetetranitramine with Water,

(2) adding to the resulting slurry with mixing an aque ous dispersion of a binder selected from the group consisting of polyamide, polyisobutylene, polytetrafluoroethylene, polyacrylate and chlorotrifiuoroethylene-vinylidene fluoride copolymer,

(3) mixing the resulting slurry of binder and explosive,

(4) adding to said slurry a coagulant selected from the group consisting of acetone, acetic acid, alum and gelatin, thereby coagulating the binder onto the explosive as Well granulated porous mix of compara tively low bulk density,

(5) adding a water-immiscible solvent for the binder selected from the group consisting of butyl alcohol, benzyl alcohol, isobutyl alcohol, butyl acetate, toluene, isobutyl acetate, xylene and methyl ethyl ketone, thereby increasing the bulk density of and softening the explosive/binder granules,

(6) hardening the granules by vaporization of the solvent from the system, and

(7) collecting the resulting hardened plastic-bonded explosive granules.

10. A process for preparing a high-bulk plastic-bonded explosive which comprises dissolving about 20 to 50 parts of low-melting, soluble-type polyamide in about 500 parts of butyl alcohol at a temperature of about -70" C., placing about 2,000 parts of water and about 470 parts of diaminotrinitrobenzene in a large still, adjusting the agitation in said still to about 500-600 rpm. and heating the resulting diaminotrinitrobenzene slurry to about 0, adding the solution of polyamide in butyl alcohol to the agitated diaminotrinitrobenzene slurry at a rate sufiicient to incorporate the polyamide into the diaminotrinitrobenzene slurry, agitating the resulting emulsion sufliciently to produce granules of diaminotrinitrobenzene/polyamide, vaporizing the butyl alcohol thereby hardening said granules, cooling the slurry to about 50 C., filtering the slurry, and collecting a plastic-bonded explosive product containing about 2 to 10 percent by weight polyamide and about 98 to percent by weight diaminotrinitrobenzene, said product having a bulk density of about 0.6 to 0.7 g./ml. and a particle size such that substantially 100 percent of the granules pass a U.S. sieve No. 18 and substantially 100 percent are retained on a :4 US. Sieve No. 80, and a compressive strength of greater than 10,000 p.s.i. when pressed at 25,000 p.s.i.g. into right cylindrical pellets of about one inch in length and one-half inch in diameter.

11. A process for the production of a high-bulk plasticbonded explosive which comprises slurrying about 470 parts of diarninotrinitrobenzene and about 4,000 parts of Water in a large still, adding to the resulting slurry about 200 to 500 parts of a percent dispersion of low-melting, soluble-type polyamide in water, thoroughly mixing the resulting aqueous slurry of diaminotrinitrobenzene and polyamide, adjusting the agitation thereof to about 300-400 r.p.rn., adding to the slurry about 2 to 3 parts of acetic acid dissolved in about 100 parts of water, thereby coagulating the polyamide, adding about 500 parts of butyl alcohol to the dispersion of coagulated polyarnide and diaminotrinitrobenzene, digesting said dispersion at about to C. for about 15 to 30 minutes, vaporizing the butyl alcohol from the system, cooling the system and filtering to collect a product containing about 2 to 10 percent by Weight polyamide and 9890 percent diaminotrinitrobenzene, having a bulk density of 0.6 to 0.7 g./m1. and a particle size such that substantially 100 percent of the granules pass a US. Sieve No. 18 and substantially 100 percent are retained on a U.S. Sieve No. 80.

12. A plastic-bonded explosive composition comprising granules consisting essentially of about 2 to 10 percent low-melting, soluble-type polyarnide and 98 to percent of an explosive selected from the group consisting of diaminotrinitrobenzene, cyclotrimethylenetrinitramine and cyclotetramethylenetetranitramine, the bulk density of said composition being from about 0.6 to about 0.7 g./ml. and the granules being of a size such that substantially 100 percent pass a US. Sieve No. 18 and substantially 100 percent are retained on a US. Sieve No. 80.

13. The composition according to claim 12 wherein the granules are in the form of pellets of about an inch in length and one-half inch in diameter and a compressive strength of greater than about 10,000 p.s.i. and a density of percent of the theoretical density.

References Cited by the Examiner UNITED STATES PATENTS 2,999,743 9/61 Breza et a1. 149-92 3,000,719 9/61 Gold et a1. 149 92 3,068,129 12/62 Schafiel 14992 XR 3,117,044 1/64 Sauer 149-92 XR CARL D. QUARFORTH, Primary Examiner.

REUBEN EPSTEIN, Examiner. 

12. A PLASTIC-BONDED EXPLOSIVE COMPOSITION COMPRISING GRANULES CONSISTING ESSENTIALLY OF ABOUT 2 TO 10 PERCENT LOW-MELTING, SOLUBLE-TYPE POLYAMIDE AND 98 TO 90 PERCENT OF AN EXPLOSIVE SELECTED FROM THE GROUP CONSISTING OF DIAMINOTRINITROBENZENE, CYCLOTRIMETHYLENETRINITRAMINE AND CYCLOTETRAMETHYLENETETRANITRAMINE, THE BULK DENSITY OF SAID COMPOSITION BEING FROM ABOUT 0.6 TO ABOUT 0.7 G./ML. AND THE GRANULES BEING OF A SIZE SUCH THAT SUBSTANTIALLY 100 PERCENT PASS A U.S. SIEVE NO. 18 AND SUBSTANTIALLY 100 PERCENT ARE RETAINED ON A U.S. SIEVE NO.
 80. 13. THE COMPOSITION ACCORDING TO CLAIM 12 WHEREIN THE GRANULES ARE IN THE FORM OF PELLETS OF ABOUT AN INCH IN LENGTH AND ONE-HALF INCH IN DIAMETER AND A COMPRESSIVE STRENGTH OF GREATER THAN ABOUT 10,000 P.S.I. AND A DENSITY OF 95 PERCENT OF THE THEORETICAL DENSITY. 